#include <fstream>
#include <deque>

using namespace std;
const int NMAX = 5000002;
using ll = long long;

ifstream cin("deque.in");
ofstream cout("deque.out");

int v[NMAX];
deque <int> dq;
int main()
{
    int n, k;
    cin >> n >> k;
    for(int i = 1; i <= n; i++)
        cin >> v[i];
    ll ans = 0;
    for(int i = 1; i <= n; i++) {
        while(!dq.empty() && v[dq.back()] > v[i])
            dq.pop_back();
        while(!dq.empty() && dq.front() <= i - k)
            dq.pop_front();
        dq.push_back(i);
        if(i >= k)
            ans += v[dq.front()];
        //cout << v[dq.front()] << " ";
    }
    cout << ans;
    return 0;
}
/*
9 3
-7 9 2 4 -1 5 6 7 1
*/